Size for gestational age at birth: impact on risk for sudden infant death and other causes of death, USA 2002.

BACKGROUND: Small for gestational age (SGA) infants have been reported to be at higher risk for sudden infant death syndrome (SIDS).
OBJECTIVE: To compare the risk of SIDS among SGA and large for gestational age (LGA) infants with that of death from other causes of sudden unexpected deaths in infancy (SUDI) and the residual "other" causes of infant death.
METHODS: The 2002 US period infant birth and death certificate linked file was used to identify infant deaths classified as SIDS (ICD-10 code R95), SUDI (ICD-10 codes R00-Y84 excluding R95) or all other residual codes. The 2002 race and sex-specific birth cohorts were used to generate the 10th and 90th percentiles of birth weight for each gestational age week from 24 to 42 weeks' gestation. Demographic variables previously identified as associated with SIDS were used in multiple logistic regression equations to determine the risk for death among SGA and LGA infants (birth weight <10th percentile and >90th percentile, respectively) independent of other potentially confounding variables.
RESULTS: Complete data on 1956 SIDS deaths, 2012 SUDI, and 11 592 other deaths were available. The adjusted OR for SIDS, SUDI and "other" causes for SGA infants was 1.65 (95% CI 1.47 to 1.85), 1.78 (1.59 to 2.00) and 4.68 (4.49 to 4.88), respectively. The adjusted OR for LGA infants was reduced for SIDS (0.73 (0.60 to 0.89)), SUDI (0.81 (0.68 to 0.98)) and "other" (0.42 (0.38 to 0.46)).
CONCLUSION: Although SGA infants seem to be at slightly increased risk for SIDS or SUDI their risk for "other" residual causes is about 2.5 times higher. LGA infants seem to be at reduced risk of mortality for all causes. The mechanisms by which restricted intrauterine growth increases risk of mortality and excessive intrauterine growth offers protective effects are uncertain.